Dynamic Changes in Implantable Collamer Lens Vault and Anterior Chamber Angle Under Varying Lighting Conditions

Matthew Hirabayashi,1,2 Eric C Cantu,1 Andrew J Abramson,3 Gurpal Virdi,4 Taj Nasser,5 Gregory Parkhurst1,2 1Parkhurst NuVision LASIK Eye Surgery, San Antonio, TX, USA; 2Amarillo NuVision, Amarillo, TX, USA; 3Texas State University, San Marcos, TX, USA; 4Mason Eye Institute, University of Missouri, Columbia, MO, USA; 5Tylock Nasser Vision, Irvine, TX, USACorrespondence: Matthew Hirabayashi, Parkhurst NuVision LASIK Eye Surgery, 9725 Datapoint Dr Suite 106, San Antonio, TX, 78229, USA, Tel +1 314 578 2374, Email matthewhirabayashi@gmail.comPurpose: To evaluate the effect of lighting conditions on Implantable Collamer Lens (ICL) vault and anterior chamber angle measurements using the MS-39, and to determine whether vault variability correlates with average vault or ICL power.Methods: A retrospective analysis was performed on 100 eyes from 53 patients who underwent EVO or EVO Toric ICL implantation. Postoperative anterior segment imaging was conducted using the MS-39 device under scotopic, mesopic, and photopic lighting. Vault and anterior chamber angles were measured, with angle values derived from the mean of the nasal and temporal readings along the 180° axis. A Friedman and ANOVA test assessed changes in measurements across lighting conditions. Pearson and Spearman correlation was used to evaluate relationships between vault variability, mean vault, and ICL power.Results: Mean vault significantly decreased under photopic conditions (393.8 ± 165.6 μm) compared to mesopic (486.7 ± 185.5 μm) and scotopic (495.6 ± 187.7 μm) states (p < 0.0001). Angle measurements increased significantly under brighter lighting (p < 0.0001). Vault variability positively correlated with mean vault (ρ = 0.395, p < 0.0001), while ICL power showed a weak negative correlation (ρ = − 0.224, p = 0.025).Conclusion: ICL vault and anterior chamber angle measurements vary meaningfully with lighting conditions. Eyes with higher vaults exhibit greater variability, while lower vaults demonstrated less variability across lighting conditions. ICL power may have a small but weak influence on vault dynamics. These findings may help refine ICL sizing strategies and postoperative assessment protocols.Keywords: refractive surgery, vision correction, phakic IOLs, vault, sizing